gistfile1.py

class Foo(object):
    
    _prop1 = None
    _prop2 = None
    _prop3 = None
    
    def set_prop1(self, value):
        self._prop1 = self._set_if_valid(value)

    def set_prop2(self, value):
        self._prop2 = self._set_if_valid(value)

    def set_prop3(self, value):
        self._prop3 = self._set_if_valid(value)
        
    def _set_if_valid(self, value):
        if value == 'hello':
            raise NameError('bad name')
        return value